The present invention relates to the field of pressure-type vacuum breaker valves.
In a system of fluid piping, in the event of a reduction or reversal of supply pressure, a pressure-type vacuum breaker valve is designed to prevent the backward siphoning of water or other fluid from an outlet towards the inlet or supply source by "breaking" or relieving the vacuum caused by the pressure decrease. In a typical vacuum breaker, a valve controls the flow of fluid through a vent for discharging fluid in the outlet if fluid pressure in the outlet exceeds atmospheric pressure. Typically, such pressure-type vacuum breakers are used to provide protection between a contaminant source and a water supply. An example of a modern piston pressure-type vacuum breaker is disclosed, for example, by U.S. Pat. No. 5,125,429 to Ackroyd et al.